Re: [PATCH] MIPS: Introduce cmdline argument writecombine=

From: Jiaxun Yang
Date: Thu Aug 06 2020 - 14:39:25 EST

在 2020/8/7 上午12:52, Thomas Bogendoerfer 写道:
On Thu, Aug 06, 2020 at 07:56:20PM +0800, Jiaxun Yang wrote:
Our current problem is Loongson's writecombine implementation seems buggy.
This is our platform issue rather than target hardware issue.
ok, so simply clear cpu_data[0].writecombine for the fauly parts

I don't know the exact faulty parts, could you please investigate it in Loongson?

I can remember a Loongson stuff told me the issue was solved in GS464E but
there are still users complaining about that.

In fact I can't reproduce it in all of my test systems:
3B1500 + RS780E + R5 230
3A3000 + RS780E Laptop
3A4000 + LS7A + RX550
And we don't even know which hardware is known to be good. The same graphic
card became a different story on different user's hand.
find out what is broken and add the needed workarounds then.

Well, let's leave this task for Loongson company.
User's community don't have the ability to trace hardware behavior precisely.

I understood what Teizhu thought. For entry-level users, we don't want to
them, so we have writecombine disabled by default. However, for advanced
trying to tweak their system, we should leave a switch for them to get it
IMHO if we do it that way, we end up with millions of knobs for tweaking
broken hardware, and nobody knows what's exactly broken. Sorry I won't go
that way.

Haha, that was my first impression to Linux as a primary school student. It just
looks like an aircraft cockpit with thousands of knobs & switches, but to airborne
you just need to control yoke and throttle.

- Jiaxun